the handbook of food engineering practice crc press chapter 10 ...

10.4.2. Examples of shelf life modeling of food products
The preceeding kinetic calculation cases show how judiciously we should use the kinetic
parameters we obtain from shelf life experiments. In most practical cases the two step
method is used due to its simplicity and convenience. The results should be understood as
mean values with possibly large confidence limits, and treated as such. Nevertheless, the
information obtained from carefully designed shelf life testing, at three or more
temperatures, is usually sufficient to allow derivation of satisfactory shelf life predicive
models. Further two examples that illustrate the use of ASLT principles and kinetic
modeling. The first, a commercially sterilized, flavored dairy beverage, sweetened with the
sweetener aspartame, is a case of straightforward use of these principles, as the quality
function of the food is defined by a dominant , quantifiable quality index, aspartame. In
contrast, the second example, of a complex food system of many antagonizing quality
deterioration modes illustrates the multidisciplinary approach and the deep knowledge of
the system required for effective shelf life testing.
10.4.2.1 Aspartame sweetened chocolate drink.
This practical example is based on experimental data generated in studies by
Bell and Labuza (1994) and Bell et al. (1994). These studies were intended to evaluate the
aspartame stability in commercially sterilized skim milk beverages of various compositions.
There is a steadily growing market for nutritious, low calorie dairy products, and aspartame
as a high intensity sweetener, without the controversy surrounding saccharin, can be a very
desirable ingredient. However, at the inherent pH of milk (6.6) the rate of aspartame
degradation is very high, reducing significantly the sensory shelf life of the product
Quantifying and modeling the behavior of this dominant quality index would allow
optimization of the product formulation and extension of shelf life, possibly by slight
alteration of the pH. For that purpose different commercially sterilized skim milks,
sweetened with 200 ppm of aspartame and slightly buffered with citrates or phosphates to
pH ranging from 6.38 to 6.67 were studied with regards to the aspartame degradation.
Samples were stored at 5 temperatures from 0 to 30° C and triplicate samples were
analyzed by HPLC, at appropriately spaced time intervals ( based on Eq.(51) and an
average Q 10 value of 4 from the literature). Results of these experiments (at pH 6.67 with
.008 M citrate) are listed in Table 9.
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